"At this time, our thoughts and prayers are with the bereaved family and we condemn this murder in the strongest possible terms," they said in a joint statement.

"There can be no justification for this brutal attack as this man was going about his daily life. People who work for the Prison Service play a crucial role in our community and any attack on them is an attack on all of us.

"Actions like this have no place in society and those who carried out this murder have nothing positive to contribute, and we refuse to let the people behind this attack divert us from building a better and peaceful future for everyone.

"We appeal to anyone with any information on this murder to contact the PSNI."

The Police Service of Northern Ireland (PSNI) chief constable Matt Baggott called for the public’s help. “This is an attack on all people and we need the full support of everyone,” said Baggott.

“Police will be increasing activity in a number of areas as a result of this murder but the most important thing is for people to remain calm, put their trust in police and work with us to catch the killers,” he added.

Forensic officers search the scene on the M1 motorway where prison officer David Black (inset) was shot as he drove near the town of Lurgan, Northern IrelandReuters/Pacemaker